Hydrophilic coloring matter for recording image, aqueous coloring agent for recording image, method and device for recording image

ABSTRACT

Image-recording, hydrophilic colorants having an organic pigment linked to a hydrophilic compound through a linking group and which are capable of forming images excellent in print quality such as chroma, gloss, density, light fastness and abrasion fastness, and also as hydrophilic colorants capable of affording inks excellent in physical properties such as long-term storability and press stability are described.

TECHNICAL FIELD

This invention relates to image-recording, hydrophilic colorants(hereinafter simply called “hydrophilic colorants”), image-recording,water-based coloring compositions (hereinafter simply called“water-based coloring compositions”), and an image-recording method andimage-recording systems making use of such hydrophilic colorants orwater-based coloring compositions.

BACKGROUND ART

In recent years, inkjet printers (hereinafter simply called “printers”)have found wide-spread commercial utility as representativeimage-recording systems making use of water-based inks (hereinaftersimply called “inks”) Reflecting the move toward high-quality printers,the use of such printers has expanded to the recording of generaldocuments, the recording of color documents, the preparation of colorNew Year's cards, the printing of color photographs, the preparation oflarge drawings, the drafting of large advertisement posters, and thelike.

Concerning the users of such printers, on the other hand, they havespread not only to office or business users but also to personal users.Keeping in step with the developments of computer-to-plates in theprinting industry field, the use of such printers has also expanded togeneral printing such as the printing of simple prints and the printingof proof sheets.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

From the foregoing background, there is an outstanding demand forhydrophilic colorants for inks, which are excellent in print qualitysuch as chroma, gloss, density and abrasion fastness when used to formimages on recording media, especially coated paper such as glossy paperand art paper and which are also excellent in physical properties suchas long-term storability and press stability when formulated into inks.

The use of an ink with water-soluble dyes contained as colorants thereinmakes it possible to obtain printed images which are good in chroma,gloss, density and the like shortly after the printing. Used as suchwater-soluble dyes include direct dyes or acid dyes, which have beenconventionally employed to dye cotton and the like or nylon and thelike.

These dyes are dissolved in water to dye cotton or nylon, so that eachof them contains one or more water-soluble groups such as sulfone groupsor carboxyl groups. As auxochromes of the dyes, these sulfone groups orcarboxyl groups directly affect chromophores and are equipped with adyeing function for fibers. From the standpoint of the light fastness ofdyed products, however, they are accompanied by a drawback that theysignificantly lower the light fastness of the dyed products. Similarly,sulfonamido groups of oil-soluble dyes also provide dyed or otherwisecolored products with considerably-lowered light fastness.

Concerning inks making use of water dispersions of pigments, on theother hand, there is a move toward incorporating the pigments in finelydivided forms in the inks to provide images, which are to be formed withthe inks, with improved vividness, brightness, color density and thelike. Even with such finely-divided pigments, however, it is still notconsidered to bring about any sufficient improving effects on the imagequality over images available from the use of dye inks.

The present inventors proceeded with extensive research to solve suchproblems. As a result, it was found that a colorant, in which ahydrophilic compound is linked with a pigment via a linking group, hassufficient solubility in an aqueous medium for an ink and also that theink with the colorant contained therein can form images pronouncedlyimproved in light fastness and the like.

To provide colorants capable of forming images excellent in printquality such as chroma, gloss, density, light fastness and abrasionfastness when employed as water-based coloring compositions, especiallyas inks for printers and also to provide hydrophilic colorants capableof affording inks excellent in physical properties such as long-termstorability and press stability, the present inventors have proceed witha further investigation on the basis of the above-described findings.The investigation has now led to the completion of the presentinvention.

Means for Solving the Problems

Described specifically, the present invention provides a hydrophiliccolorant represented by the following formula (1):(organic pigment)-(linking group)-(hydrophilic compound)  (1)wherein said organic pigment is a hydrophobic pigment having nohydrophilic group by itself, said linking group is a group linking saidorganic pigment and said hydrophilic compound with each other andblocking an effect of said hydrophilic compound on said organic pigment,and said hydrophilic compound is an anionic, cationic and/or nonionic,hydrophilic compound.

In the above-described hydrophilic colorant according to the presentinvention, the hydrophobic pigment can be selected preferably from thegroup consisting of phthalocyanine, anthraquinone, perylene, perinone,dioxazine, quinacridone, diketopyrrolopyrole, indigo• thioindigo,quinophthalone, isoindolinone, metal complex, azo, high-molecular azo,azomethine-containing azo, and azomethine pigments; and/or the linkinggroup can be selected preferably from the group consisting of analkylene group, s-triazinyl group, s-triazinyl-2,4-diamino group,s-triazinyl-2,4-dioxy group, s-triazinyl-2-amino-4-oxy group,s-triazinyl-2,4-diaminoalkyl group, and s-triazinyl-2-aminoalkyl-4-oxygroup.

The present invention also provides a water-based coloring compositioncomprising the above-described hydrophilic colorant of the presentinvention and an aqueous medium; an image-recording method, whichcomprises using the above-described hydrophilic colorant of the presentinvention or the above-described water-based coloring composition of thepresent invention; an image-recorded medium obtained by theimage-recording method; and an image-recording system comprising theabove-described hydrophilic colorant of the present invention or theabove-described water-based coloring composition of the presentinvention loaded as an image-recording material therein. As therecording system, an inkjet printer is preferred.

Advantageous Effects of the Invention

According to the present invention, it is possible to provide colorantscapable of forming images excellent in print quality such as chroma,gloss, density, light fastness and abrasion fastness when employed aswater-based coloring compositions, especially as inks for printers andalso to provide hydrophilic colorants capable of affording inksexcellent in physical properties such as long-term storability and pressstability.

BEST MODES FOR CARRYING OUT THE INVENTION

Based on certain preferred embodiments, the present invention willhereinafter be described in further detail. The term “organic pigment”,which characterizes the present invention, means a hydrophobic pigmentcontaining no hydrophilic group by itself and having a large molecularweight, specifically an organic pigment selected from the groupconsisting of phthalocyanine, anthraquinone, perylene, perinone,dioxazine, quinacridone, diketopyrrolopyrole, indigo• thioindigo,quinophthalone, isoindolinone, metal complex, azo, high-molecular azo,azomethine-containing azo, and azomethine pigments.

Conventionally, the light fastness of a pigments has been indicated by arating of from 8 to 1 or by a class of E, VG, G, F or P. Pigments usefulin the present invention can be those of Rating 6 or Class G or higher,preferably those of Rating 7 or Class VG or higher, more preferablythose of Rating 8 or Class E of higher. The light fastness of a pigmentis determined by the molecular structure of the pigment or thecrystallinity of the pigment. The present invention uses a pigment, thelight fastness of which is considered to be superb based on itsmolecular structure, to obtain a hydrophilic colorant of the presentinvention having high light fastness. Pigments preferred in the presentinvention are, therefore, those which contain one or more substituentgroups permitting the introduction of the above-described linking groupor groups and have high light fastness.

Examples of the above-described preferred pigments include, asphthalocyanine pigments, copper phthalocyanine blue (C.I. Pigment Blue15), aluminum phthalocyanine blue, metal-free phthalocyanine blue (C.I.Pigment Blue 16), partially-brominated copper phthalocyanine green,partially-chlorinated copper phthalocyanine green, and the like.

As anthraquinone pigments, phthalolylamide yellow (C.I. Pigment Yellow123), flavanthrone (C.I. Pigment Yellow 24), anthrapyrimidine yellow(C.I. Pigment Yellow 108), C.I. Vat Yellow 48, pyranthrone orange (C.I.Pigment Orange 40), C.I. Pigment Red 177, dibromoanthoanthrone (C.I.Pigment Red 168), indanthrone blue (C.I. Pigment Blue 60) and the likecan be mentioned.

As perylene pigments, perylene red 189 (C.I. Pigment Red 189), perylenered 190 (C.I. Pigment Red 190), C.I. Pigment Red 149 and the like can bementioned. As perinone pigments, perinone orange (C.I. Pigment Orange43), perinone red (C.I. Pigment Red 194) and the like can be mentioned.

As dioxazine pigments, dioxazine violet (C.I. Pigment Violet 23) and thelike can be mentioned, and as quinacridone pigments, quinacridone red(C.I. Pigment Violet 19), quinacridone magenta (C.I. Pigment Red 122),dichloroquinacridone (C.I. Pigment Red 209) and the like can bementioned.

As diketopyrrolopyrole pigments, diketopyrrolopyrole reds (C.I. PigmentRed 254 and 255) and the like can be mentioned, and as indigo•thioindigopigments, thioindigo red (C.I. Pigment Red 87), thioindigo magenta (C.I.Pigment Red 87), dichlorodimethylthioindigo (C.I. Pigment Violet 36) andthe like can be mentioned.

As quinophthalone pigments, quinophthalone yellow (C.I. Pigment Yellow138) and the like can be mentioned, and as isoindolinone pigments,isoindolinone yellow (C.I. Pigment Yellow 139), C.I. Pigment Yellow 109and the like can be mentioned.

As metal complex pigments, nickel nitroso yellow (C.I. Pigment Yellow153) and the like can be mentioned. Further, colorants having similarchemical formulas to the above-described various higher pigments can bementioned.

The term “linking group” as used herein means a group having functionsthat a hydrophilic compound is linked to the above-described pigment andeach water-soluble group, such as a sulfone or carboxyl group, in thehydrophilic compound is blocked from affecting the pigment such that thehue or light fastness of the pigment is altered or lowered due to achange in pH. The linking group can be selected, for example, from analkylene group (preferably of 1 to 30 carbon atoms), s-triazinyl group,s-triazinyl-2,4-diamino group, s-triazinyl-2,4-dioxy group,s-triazinyl-2-amino-4-oxy group, s-triazinyl-2,4-diaminoalkyl group,s-triazinyl-2-aminoalkyl-4-oxy group, or the like.

The term “hydrophilic compound” as used herein means aconventionally-known compound having one or more anionic, cationicand/or nonionic, hydrophilic groups. Illustrative are compounds havingone or more anionic groups such as carboxyl, sulfone, sulfate ester orphosphate ester groups; one or more cationic groups such as primary totertiary amino or quaternary ammonium groups; one or more nonionicgroups such as alcoholic hydroxyl, polyethylene glycol or polyethyleneglycol monoalkyl ether groups; or one or more anionic•nonionic groupssuch as polyethylene glycol monophthalate, polyethylene glycolmonosulfate or polyethylene glycol monophosphate.

As illustrative groups of the above-described hydrophilic compounds eachof which can be introduced into the pigment via the linking group,groups of the following compounds can be mentioned.

(1) Groups of hydrophilic compounds the linking groups of which arealkylene groups:

-   The disodium salt of a trimellitic acid monoamidomethylene group,    the monosodium salt of a phthalic monoamidomethylene group, the    sodium salt of a carboxymethylaminomethylene group, the disodium    salt of a di(carboxymethyl)aminomethylene group, the disodium salt    of a (glutalic acid)-1-iminomethylene group derived from glutamic    acid, the disodium salt of a (succinic acid)-1-iminomethylene group    derived from aspartic acid, the disodium salt of a trimellitic acid    monoamidoethylene group, the monosodium salt of a phthalic acid    monoamidoethylene group, the disodium salt of a trimellitic acid    monoamidoproylene group, the monosodium salt of a phthalic acid    monoamidopropylene group, the disodium salt of a sulfosuccinic acid    monoamidomethylene group, the disodium of a sulfophthalic acid    monoamidomethylene group, the monosodium salt of a trimellitic acid    (methoxypolyethylene glycol monoester) monoamidomethylene group, and    the like.

(2) Groups of hydrophilic compounds the linking groups of which ares-triazinyl groups:

-   The tetrasodium salt of a    4,6-bis(3′,4′-dicarboxyphenylenamino)-s-triazinyl-2-amino group, the    disodium salt of a    4,6-bis(4′-carboxyphenylamino)-s-triazinyl-2-amino group, the    disodium salt of a 4,6-bis(carboxymethylamino)-s-triazinyl-2-amino    group, the tetrasodium salt of a    4,6-bis[di(caboxymethyl)amino]-s-triazinyl-2-amino group, the    disodium salt of a 4,6-bis(propionic    acid-1-amino)-s-triazinyl-2-amino group, the tetrasodium salt of a    4,6-bis(glutalic acid-1-amino)-s-triazinyl-2-amino group, the    tetrasodium salt of a 4,6-bis(succinic    acid-1-amino)-s-triazinyl-2-amino group, the disodium salt of a    4,6-bis (sulfoethylamino)-s-triazinyl-2-amino group, the disodium    salt of a 4,6-bis(N-methyl-sulfoethylamino)-s-triazinyl-2-amino    group, a 4,6-bis(polyoxyethylenamino)-s-triazinyl-2-amino group, the    tetrasodium salt of a    4,6-bis(3′,4′-dicarboxyphenylenamino)-s-triazinyl-2-oxy group, the    disodium salt of a 4,6-bis(carboxymethylamino)-s-triazinyl-2-oxy    group, the tetrasodium salt of a    4,6-bis(3′,4′-dicarboxyphenylenamino)-s-triazinyl-2-aminoethyl    group, the tetrasodium salt of a    4,6-bis[di(carboxymethyl)amino]-s-triazinyl-2-aminomethyl group, and    the like.

The following processes can be mentioned as illustrative processes forthe synthesis of the hydrophilic colorant in the present invention.

-   (1) A process comprising reacting a polyfunctional, reactive    compound, which can form a linking group, with a pigment or a    derivative thereof; reacting a hydrophilic compound (or a precursor    of the hydrophilic compound, said precursor containing a latent    hydrophilic group) which is reactive with the reaction product; and    in the case of the precursor, converting the latent hydrophilic    group into a hydrophilic group;-   (2) A process comprising reacting a hydrophilic compound or a    precursor thereof with a polyfunctional, reactive compound which can    form a linking group; and then reacting the resulting reaction    compound with a pigment or a derivative thereof; and-   (3) A process comprising reacting a hydrophilic compound or a    precursor thereof with a pigment intermediate or a derivative    thereof via a polyfunctional compound capable of forming a linking    group; and using the resulting reaction compound to obtain a    pigment.

Further, examples of the above-described individual production processeswill be described specifically.

The Process (1)

For example, cyanuric chloride is reacted beforehand with 2 molarequivalents of iminodiacetic acid and 1 molar equivalent of ammonia tosynthesize 2-amino-4,6-bis(dicarboxymethylamino)-s-triazine. A copperphthalocyanine blue pigment is dissolved in concentrated sulfuric acid,and paraformaldehyde is reacted to synthesize a methylol-substitutedproduct. The 2-amino-2-amino-4,6-bis(dicarboxymethylamino)-s-triazinewhich has been obtained in the above is then reacted to synthesize4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl copperphthalocyanine. The carboxyl groups are then neutralized with an aqueoussolution of sodium hydroxide to obtain4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl copperphthalocyanine sodium. In the above-described hydrophilic colorant, thes-triazinylaminomethyl group is a linking group and has a function tolink the sodium carboxylate group, in which a carboxymethylamino groupis a hydrophilic group, such that the pigment is solubilized. The numberof 4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl group(s) canbe changed depending upon the molar ratio to be reacted. In the case ofa copper phthalocyanine, the solubilization of a hydrophilic colorantderived from the copper phthalocyanine requires about 3 to 4 or moresubstituent groups of the sodium carboxylate on average per molecule ofthe hydrophilic colorant. With respect to other pigments, hydrophiliccolorants according to the present invention can also be synthesized byreacting them in a similar manner as described above.

The Process (2)

For example, formaldehyde is reacted with trimellitamide to synthesize amethylol-substituted product. A copper phthalocyanine blue pigment isdissolved in concentrated sulfuric acid, and is reacted with themethylol-substituted product of trimellitamide to synthesizetrimellitimidomethyl copper phthalocyanine. The imido group was thenhydrolyzed with an aqueous solution of sodium hydroxide to affordtrimellitamidomethyl copper phthalocyanine sodium. In theabove-described hydrophilic colorant, the methylene group forms alinking group, and the trimellitamido (dicarboxybenzamido) group linksthe sodium carboxylate group as a hydrophilic group to solubilize thepigment. The number of trimellitamidomethylene group(s) can be changeddepending upon the molar number of the raw material to be reacted.Examples of the latent hydrophilic group in the precursor having thelatent hydrophilic group include lower alkyl(C1–3) carboxylate groupsand carboxylamido groups. With respect to other pigments, hydrophiliccolorants can also be synthesized by reacting them in a similar manneras described above.

As an alternative synthesis process, cyanuric chloride is reacted with 2molar equivalents of iminodiacetic acid (or its dimethyl ester) tosynthesize 2-chloro-4,6-bis(dicarboxymethylamino)-s-triazine (or itsdimethyl ester). The chlorine in the resulting triazine derivative isreacted with an amino group in an amino-containing pigment, for example,the amino group in Pigment Red 177 to afford a hydrophilic colorant of ared color. Further, the chloride is reacted with the imino groups inperylenetetracarboxylic bis(aminophenylimide) (and in the case of thedimethyl ester, then hydrolyzed) to obtain a hydrophilic colorant of ared color. In the above-described hydrophilic colorant, thes-triazinylamino group acts as a linking group and links the sodiumcarboxylate group.

The Process (3)

For example,2,4-bis(dicarboxymethylamino)-6-(amino)phenylamino-s-triazine is reactedwith perylenetetracarboxylic acid anhydride to obtain a hydrophiliccolorant of a red color. Further,2′,4′-bis(dibutoxycarbonylamino)-s-triazinyl-6′-(4-amino)phthalodinitrileand phthalodinitrile are reacted at a molar ratio of 2:2 together withcopper chloride in accordance with the phthalodinitrile process toafford a copper phthalocyanine derivative. The derivative is subjectedto alkali hydrolysis to obtain the sodium salt of2′,4′-bis(dicarboxymethylamino)-s-triazinyl-6′-(4-amino)copperphthalocyanine. In the above-described hydrophilic colorant, thes-triazinylamino group acts as a linking group to link the sodiumcarboxylate group.

As particularly preferred hydrophilic colorants in the presentinvention, colorants represented by the following formula (2) or (3) canbe mentioned.

wherein P represents an organic pigment molecule, M represents ahydrogen atom, alkali metal, ammonium group, (lower alkyl)ammonium groupor (lower alkanol)ammonium group, and n stands for 1 to 4. Examples ofthe above-described pigment include a copper phthalocyanine pigment(C.I. Pigment Blue 15), a quinacridone pigment (C.I. Pigment Violet 19),a flavanthrone pigment (C.I. Pigment Yellow 24), and the like.

The water-based coloring composition according to the present inventionis characterized in that it comprises the above-described hydrophiliccolorant of the present invention and an aqueous medium. Suitableexamples of the water-based coloring composition are inks for ink-jetprinting. In terms of hues, such inks include 3-color inks consisting ofcyan, magenta and yellow, 5-color inks added further with sky blue andpink colors, 6-color inks obtained by adding orange, green and violetcolor inks to the 3-color inks, and ink combinations with a black inkadded further to such inks. These inks each contains one or more of theabove-described hydrophilic colorants as colorants.

The ink according to the present invention contains the hydrophiliccolorant at a content sufficient to fully provide printed images withsatisfactory print quality such as color density, chroma and gloss andalso to provide the printed images with satisfy dryability and fastnesssuch as abrasion fastness. In addition, this content should also besufficient to provide the ink with satisfactory viscosity and storagestability. From these requirements, the content of the hydrophiliccolorant can be from 0.5 to 20 wt. %, preferably from 1 to 10 wt. %.

To make further improvements in physical properties of the resulting inksuch as abrasion fastness and also in print quality such as printdefinition and gloss, a hydrophilic polymer may be incorporated in theink according to the present invention as needed. Preferred as such ahydrophilic polymer can be a conventionally-known, alkali-solublepolymer which has been used in inks for years. This preferred,alkali-soluble polymer acts not only as a dissolution aid for thehydrophilic colorant in the ink but also as a binder for the hydrophiliccolorant. No particular limitation is imposed on such a hydrophilicpolymer insofar as it is a polymer soluble in an aqueous solution of analkali. However, use of a polymer the weight average molecular weight ofwhich is 50,000 or lower, preferably 40,000 or lower is preferred fromthe standpoint of the dissolution stability of the hydrophilic colorantin the ink.

As the hydrophilic polymer, a hydrophilic random copolymer, hydrophilicgraft copolymer, hydrophilic block copolymer or the like, which iscomposed of a hydrophilic monomer and a hydrophobic monomer, can bementioned. Examples of the hydrophilic monomer includeα,β-ethylenically-unsaturated carboxylic acids such as (meth)acrylicacid and crotonic acid, and their ethylene glycol esters, polyethyleneglycol esters, alkoxypolyethylene glycols, and the like; unsaturateddibasic acids such as maleic acid, fumaric acid and itaconic acid, andtheir half alkyl(C1–8) esters, half amides, di(ethylene glycolmonoesters), di(polyethylene glycol monoesters), di(alkoxypolyethyleneglycol esters), and the like; styrenesulfonic acid; and vinyl sulfonicacid. Examples of the hydrophobic monomer, on the other hand, includestyrene, and styrene derivatives such as α-methylstyrene;vinylnaphthalene derivatives; aliphatic, alicyclic or aromatic alcoholesters of α,β-ethylenically-unsaturated carboxylic acids, such asaliphatic, alicyclic or aromatic alcohol(C1–C30) esters andalkoxy(C1–C4) or alkyl(C2–C4) esters of (meth)acrylic acid; aliphatic,alicyclic or aromatic alcohol(C1–C30) diesters of unsaturated dibasicacids such as maleic acid, fumaric acid and itaconic acid; and vinylacetate, butadiene, isoprene, ethylene, propylene, and butylene.

In the above-described hydrophilic polymer, one or more comonomers canalso be used as desired. Illustrative are (meth)acrylonitrile,(meth)acrylamide, N-methylol (meth)acrylamide, and diacetone acrylamide.The content of the hydrophilic polymer in the ink may be preferably from5 to 100 wt. %, more preferably from 8 to 50 wt. % based on the contentof the hydrophilic colorant. An alkali is used to solubilize such ahydrophilic polymer in an aqueous medium. Although no particularlimitation is imposed on the alkali, a preferred alkali can be, forexample, a compound selected from the group consisting of ammonia,primary, secondary and tertiary organic amines (including basic,nitrogen-containing, heterocyclic compounds), and alkali metalhydroxides such as sodium hydroxide and potassium hydroxide.

An aqueous medium suitable for use in the ink according to the presentinvention is water or a mixed solvent of water and a water-solubleorganic solvent. As the water, use of deionized water is preferred. Thecontent of water in the ink is generally in a range of from 10 to 70 wt.%, with a range of from 20 to 50 wt. % being preferred. A water-solubleorganic solvent can also be used for its function to prevent the inkfrom drying and also to promote the dissolution of the colorant.Illustrative are alkylene polyols in each of which the alkylene groupcontains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol,butylene glycol, thiodiglycol, hexylene glycol, diethylene glycol,triethylene glycol, 1,2,6-hexanetriol and glycerin; lower alkyl ethersof polyhydric alcohols, such as ethylene glycol monoalkyl (C1–C4)ethers, diethylene glycol alkyl (C1–C4) ethers) and triethylene glycolmonoalkyl (C1–C4) ethers; N-methyl-2-pyrrolidone; 2-pyrrolidone; and1,3-dimethyl-2-imidazolidinone. To control the drying characteristics ofthe ink or to improve the solubility of a material to be added such as ahydrophilic polymer, an alkyl alcohol having 1 to 4 carbon atoms, suchas n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butylalcohol or tert-butyl alcohol, can also be added to the ink as needed.To provide an ink having desired physical properties, one or more ofother components such as surfactants, defoaming agents and preservativescan also be added to the ink of the present invention as needed. Inaddition, urea, thiourea or ethylene urea or a derivative thereof canalso be incorporated as a drying preventive for the ink at nozzles.

Any dissolution apparatus can be used to dissolve the hydrophiliccolorant in the aqueous medium in the present invention, insofar as itis a commonly-employed dissolution apparatus. Dissolution can beeffected, for example, in a conventionally-known dissolution apparatussuch as a dissolution tank equipped with an agitator and permittingheating and cooling or a reactor equipped with an agitator andcondenser. Subsequent to the dissolution, it is also possible to performa step such as the removal of undissolved components by a filter, acentrifugator or the like.

The hydrophilic colorant according to the present invention can also beused in the form of an admixture with a water dispersion of fineparticles of a pigment or a sulfonated pigment, said fine particles orsulfonated pigment having been conventionally used as a colorant forinks, especially with a sulfonated, carbon black pigment (seeJP-A-2003-165926). In combination with one or more inks containing theabove-described conventional colorants, one or more inks withhydrophilic colorants of the present invention contained therein can beused as an ink of a single color or inks of plural colors in 4-color to7-color inks to provide a set of inks.

The ink according to the present invention is excellent in colordevelopment properties such as color density and chroma and also superbin print quality, and is suited especially for inkjet recording thatperforms recording by causing ink droplets to fly from a printer head.The hydrophilic colorant according to the present invention, on theother hand, is suited as a wet developer for wet electroprinting, acolorant for printing inks such as water-based gravure inks andwater-based flexographic inks, a colorant for paper, a colorant intextile printing agents for woven fabrics, and the like.

EXAMPLES

Based on specific examples and comparative examples, the presentinvention will next be described in further detail. It is, however, tobe noted that all the designations of “part”, “parts” and “%” in thefollowing description are on a weight basis unless otherwisespecifically indicated.

Example 1

(a) Preparation of Hydrophilic Colorant Solutions

Trimellitimide was dissolved in concentrated sulfuric acid, followed bythe reaction with 1.2 molar equivalents of paraformaldehyde tosynthesize a methylol-substituted product. A copper phthalocyanine bluepigment (C.I. Pigment Blue 15) was added to and dissolved in thereaction mixture to react it with the methylol-substituted product oftrimellitimide. The reaction mixture was poured into a large amount ofice water to have the reaction product precipitated. The reactionproduct was collected by filtration, and was then washed to obtaintrimellitimidomethyl copper phthalocyanine. Following a conventionalprocedure, an aqueous solution of sodium hydroxide was added to conducta hydrolytic reaction, and thereafter, undissolved matter was filteredout. The resulting, blue aqueous solution of trimellitamidomethyl copperphthalocyanine sodium was added to dilute acetic acid to acidify thesolution such that reprecipitation was induced. The precipitate waswashed with water and then dried to afford thetrimellit(monoamido)methyl derivative of copper phthalocyanine. Thedegree of substitution was approximately 2.5 (hereinafter called “theblue pigment derivative-1”).

The trimellit(monoamido)methyl derivative of quinacridone (hereinaftercalled “the red pigment derivative-1”) was also obtained in a similarmanner except that a quinacridone pigment (C.I. Pigment Violet 19) wasreacted in place of the copper phthalocyanine blue pigment.

The trimellit(monoamido)methyl derivative of flavanthrone (hereinaftercalled “the yellow pigment derivative-1”) was also obtained in a similarmanner except that a flavanthrone pigment (C.I. Pigment Yellow 24) wasreacted.

(b) Preparation of Printer Inks

A dried product (10 parts) of the blue pigment derivative-1 was taken,and then added to an aqueous alkali solution (80 parts) which containedsubstantially the equivalent amount of sodium hydroxide, and theresultant mixture was stirred. While paying attention to the pH, anaqueous alkali solution was added, followed by stirring for 1 hour todissolve the blue pigment derivative-1. Subsequent to the dissolution,the pH was adjusted to from 8.0 to 8.5. The resulting mixture wassubjected to centrifugation to adjust the concentration of the bluepigment derivative-1 to 10%. To the thus-obtained 10% aqueous solutionof the colorant (60 parts), a mixture (40 parts) consisting of ethyleneglycol (10 parts), glycerin (20 parts), “SURFYNOL 82” (product of AirProducts and Chemicals, Inc.) (1 part) and water (9 parts) was added.After thorough stirring, the mixture was filtered through a membranefilter of 5 μm pore size to obtain a cyan ink for printers.

A magenta ink for printers and a yellow ink for printers were alsoprepared in a similar manner except that in place of the blue pigmentderivative-1, the red pigment derivative-1 and the yellow pigmentderivative-1 were used to prepare a 10% aqueous solution of the magentacolorant and a 10% aqueous solution of the yellow colorant,respectively.

(c) Ranking of the Printer Inks

Each of the inks obtained in the above-described procedure (b) wereranked as will be described hereinafter. The ink was filled in an inkcartridge, and by a printer, solid printing was performed on glossyinkjet paper, “PHOTOLIKE QP” (product of KONICA CORPORATION). After theprint was left over for 1 day in a room, its optical density wasmeasured using “MACBETH RD-914” (manufactured by Macbeth AG), its chromawas measured using a chromatic meter (“CR-321”, manufactured by MinoltaCamera Co., Ltd.), and its 60-deg. gloss was measured using“MICRO-TRI-GLOSS” (manufactured by BYK-Chemie GmbH). Further, verticaland horizontal lines were printed. The resultant print was visuallyobserved for print definition to rank its print quality. To performranking in light fastness, the print was exposed to ultraviolet rays atan irradiation intensity of 60 mW/cm² and a temperature of 63° C. for 15hours in an accelerated light-fastness tester (“I-SUPER UV TESTER”,manufactured by Iwasaki Electric Co., Ltd.). The optical density andchroma of the print were measured both before and after the test. Theresults are shown in Table 1.

TABLE 1 Inks of Example 1 Cyan Magenta Yellow Quality of Print Opticaldensity 2.55 1.92 2.04 printed quality Chroma 60.8 76.2 90.5 image Printdefinition A A A 60-Deg. gloss 99 105 103 Light Optical Before test 2.551.92 2.04 fastness density After test 2.50 1.33 1.85 Chroma Before test60.8 76.2 90.5 After test 55.4 56.4 70.6 Ranking in print definition -A: No misalignment, B: Substantially no misalignment, C: Misaligned.

Comparative Example 1

Using commercial dye inks, their ranking was performed in a similarmanner as in Example 1(c). The results are shown in Table 2.

TABLE 2 Inks of Comparative Example 1 Cyan Magenta Yellow Quality ofPrint Optical density 2.51 2.06 2.24 printed quality Chroma 55.3 83.4118 image Print definition A A A 60-Deg. gloss 45 52 53 Light OpticalBefore test 2.51 2.06 2.24 fastness density After test 2.29 0.21 0.90Chroma Before test 55.3 83.4 118 After test 49.4 12.8 62.2 Ranking inprint definition - A: No misalignment, B: Substantially no misalignment,C: Misaligned.

As evident from Tables 1 and 2, the inks according to the presentinvention were equivalent to the commercial dye inks in print qualitysuch as optical density, chroma and print definition, and were farsuperior to the dye inks in the gloss and light fastness of prints.

Example 2

(a) Preparation of Hydrophilic Colorant Solutions

The copper phthalocyanine blue pigment was dissolved in concentratedsulfuric acid, followed by the reaction with 2 molar equivalents ofparaformaldehyde to synthesize a methylol-substituted product.2-Amino-4,6-bis(dicarboxymethylamino)-s-triazine was then reacted tosynthesize 4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl copperphthalocyanine. The carboxyl groups were neutralized with an aqueoussolution of sodium hydroxide to effect dissolution. Undissolved matterwas filtered out. The resulting, blue aqueous solution of4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl copperphthalocyanine sodium was added to dilute acetic acid to acidify thesolution such that the colorant was caused to reprecipitate. Theprecipitate was washed with water and then dried to afford4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl copperphthalocyanine. The degree of substitution was approximately 1.5(hereinafter called “the blue pigment derivative-2”).

The 4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl derivative ofquinacridone (hereinafter called “the red pigment derivative-2”) wasalso obtained in a similar manner except that a quinacridone pigment(C.I. Pigment Violet 19) was reacted in place of the copperphthalocyanine blue pigment. The4′,6′-bis(dicarboxymethylamino)-s-triazinylaminomethyl derivative offlavanthrone (hereinafter called “the yellow pigment derivative-2”) wasalso obtained in a similar manner except that a flavanthrone pigment(C.I. Pigment Yellow 24) was reacted.

(b) Preparation of Printer Inks

A dried product (20 parts) of the blue pigment derivative-2 was added toan aqueous alkali solution (80 parts) which contained substantially theequivalent amount of sodium hydroxide, and the resultant mixture wasstirred. While paying attention to the pH, an aqueous alkali solutionwas added, followed by stirring for 1 hour to effect dissolution.Subsequent to the dissolution, the pH was adjusted to from 8.0 to 8.5.The resulting mixture was subjected to centrifugation to adjust theconcentration to 15%. To the thus-obtained 15% aqueous solution of thecolorant (60 parts), a mixture (40 parts) consisting of ethylene glycol(10 parts), glycerin (20 parts), “SURFYNOL 82” (product of Air Productsand Chemicals, Inc.) (1 part) and water (9 parts) was added. Afterthorough stirring, the mixture was filtered through a membrane filter of5 μm pore size to obtain a cyan ink for printers.

A magenta ink for printers and a yellow ink for printers were alsoprepared in a similar manner except that in place of the blue pigmentderivative-2, the red pigment derivative-2 and the yellow pigmentderivative-2 were used to prepare a 15% aqueous solution of the magentacolorant and a 15% aqueous solution of the yellow colorant,respectively.

(c) Ranking of the Printer Inks

Each of the inks obtained in the above-described procedure (c) wasranked by the methods described in Example 1. The results are shown inTable 3.

TABLE 3 Inks of Example 2 Cyan Magenta Yellow Quality of Print Opticaldensity 2.23 2.03 2.16 printed quality Chroma 62.5 80.4 92.4 image Printdefinition A A A 60-Deg. gloss 100 99 96 Light Optical Before test 2.232.03 2.16 fastness density After test 1.90 1.70 1.86 Chroma Before test62.5 80.4 92.4 After test 55.4 50.2 68.3 Ranking in print definition -A: No misalignment, B: Substantially no misalignment, C: Misaligned.

As evident from Table 3, the inks according to the present inventionwere equivalent to the commercial dye inks in print quality such asoptical density, chroma and print definition, and were far superior tothe dye inks in the gloss and light fastness of prints.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide colorantscapable of forming images excellent in print quality such as chroma,gloss, density, light fastness and abrasion fastness when employed aswater-based coloring compositions, especially as inks for printers andalso to provide hydrophilic colorants capable of affording inksexcellent in physical properties such as long-term storability and pressstability.

1. An image-recording, hydrophilic colorant represented by the followingformula (1):(organic pigment)−(linking group)−(hydrophilic compound)  (1) whereinthe organic pigment is a hydrophobic pigment selected from the groupconsisting of perinone, dioxazine, quinacridone, diketopyrrolopyrole,quinophthalone, isoindolinone, and metal complex; the linking group isselected from the group consisting of an alkylene group. s-triazinylgroup. s-triazinyl-2.4-diamino group. s-triazinyl-2.4-dioxy group.s-triazinyl-2-amino-4-oxy group, s-triazinyl-2.4-diaminoalkyl group, ands-triazinyl-2-aminoalkyl-4-oxy group; and the hydrophilic compoundcomprises one or more carboxyl groups, sulfone groups, sulfate estergroups, phosphate ester groups, primary amino groups, primary quaternaryammonium groups, secondary amino groups, secondary quaternary ammoniumgroups, tertiary amino groups, tertiary quaternary ammonium groups;alcoholic hydroxyl groups, polyethylene glycol grouos, polyethyleneglycol monoalkyl ether groups; polyethylene glycol, monophthalate,polyethylene glycol monosulfate or polyethylene glycol monophosphate 2.An image-recording, water-based coloring composition comprising thehydrophilic colorant according to claim 1 and an aqueous medium.
 3. Animage-recording method, comprising forming an image with a composition,which comprises the hydrophilic colorant according to claim
 1. 4. Animage-recorded medium obtained by the image-recording method accordingto claim
 3. 5. An image-recording system comprising the hydrophiliccolorant according to claim 1 loaded as an image-recording materialtherein.
 6. An image-recording system according to claim 5, which is aninkjet printer.
 7. An image-recording method, comprising forming animage with a composition, which comprises the water-based coloringcomposition according to claim
 2. 8. An image-recorded medium obtainedby the image-recording method according to claim
 7. 9. Animage-recording system comprising the water-based coloring compositionaccording to claim 2, loaded as an image-recording material therein. 10.An image-recording system according to claim 9, which is an inkjetprinter.
 11. A hydrophilic colorant which is represented by thefollowing formula (2):

wherein P represents an organic pigment molecule, M represents ahydrogen atom, alkali metal, ammonium group, (lower alkyl)ammonium groupor (lower alkanol)ammonium group, and n stands for 1 to
 4. 12. Animage-recording, water-based coloring composition comprising thehydrophilic colorant according to claim 11 and an aqueous medium.
 13. Animage-recording method, comprising forming an image with a composition,which comprises the hydrophilic colorant according to claim
 11. 14. Animage-recorded medium obtained by the image-recording method accordingto claim
 13. 15. An image-recording system comprising the hydrophiliccolorant according to claim 11 loaded as an image-recording materialtherein.
 16. A hydrophilic colorant, which is represented by thefollowing formula (3):

wherein P represents an organic pigment molecule, M represents ahydrogen atom, alkali metal, ammonium group, (lower alkyl)ammonium groupor (lower alkanol)ammonium group, and n stands for 1 to
 4. 17. Animage-recording, water-based coloring composition comprising thehydrophilic colorant according to claim 16 and an aqueous medium.
 18. Animage-recording method, comprising forming an image with a composition,which comprises the hydrophilic colorant according to claim
 16. 19. Animage-recorded medium obtained by the image-recording method accordingto claim
 18. 20. An image-recording system comprising the hydrophiliccolorant according to claim 16 loaded as an image-recording materialtherein.